1. Field of the Invention
The present invention relates to a robot cleaner, and more particularly to a driving apparatus for a robot cleaner having a driving unit capable of dealing with thresholds or obstacles.
2. Description of the Prior Art
In general, a robot cleaner performs cleaning jobs alone without users' commands. Such a robot cleaner is mainly used indoor, so it has lot of occasions coming across obstacles such as thresholds, carpet, or the like. For these occasions, a damping unit is provided to have drive wheels in contact with floor all the time and to reduce shock transferring to the main body of the robot cleaner.
FIG. 1 to FIG. 3 are views for showing a driving apparatus for a robot cleaner, disclosed in PCT WO 02/067744, in which a damping unit is provided.
As shown in FIG. 1 to FIG. 3, a robot cleaner is sealed in a circular housing 10. A filter container (not shown) is mounted inside the housing 10 to accommodate collected dirt such as dust and the like therein. Further, two drive wheels 12 are installed diametrically opposite to each other inside the robot cleaner. Each drive wheel 12 is rotatably mounted on a drive wheel shaft 13, and in front and rear of which two supporting parts, that is, rear rollers 14 and front rollers 15 are mounted. The rear rollers 14 are in contact with floor, help the robot cleaner to operate, and are installed at each side of a central axis directed in the movement direction of the robot cleaner. Further, the front rollers 15 are mounted in front of the drive wheel shaft 13. The supporting parts provided with the front and rear rollers 14 and 15 create a gap between the floor and the bottom surface of the robot cleaner, so the bottom surface of the robot cleaner is prevented from being a direct contact with the floor.
The two drive wheels 12 are formed of materials having a high friction coefficient, and, as shown in FIG. 2 and FIG. 3, mounted to a drive wheel support 16. The drive wheel support 16 is connected to an electric motor 17 and a transmission 18.
The drive wheel support 16 reduces vertical movements of the housing 10, in which an upwardly directed part 20 is engaged with a slide bearing 21 by screws for supporting the wheels 12 in the vertical direction, and the sliding bearing 21 can reciprocate in upward and downward directions by the slide rail 22.
The slide bearing 21 and the slide rail 22 are disposed between upper and lower wall parts 23 and 24, and a dowel 25 restrains the slide bearing 21 and the slide rail 22, the upper end of the dowel 28 connected to the spring coil 26 and a collar 27 rests in a seat 29 provided in the upper wall part 23, so that the dowel 28 can play a damping role.
In the meantime, the transmission 18 is provided with an extension arm 34, and slidably coupled with a bracket 36 on which two micro switches 35 connected to a lower wall part 24 are installed. The micro switches 35 are activated when the wheels 12 become spaced from the floor due to a shape of the floor or obstacles, notifying a certain control unit of whether the wheels 12 are in contact with the floor.
However, as shown in FIG. 1 to FIG. 3, the drive wheel support 16 provided to the drive wheels 12 provides only a small range of ascending and descending motion as the robot cleaner comes across obstacles or thresholds. Accordingly, as one drive wheel 12 rolls over a hole on the floor or a slanted place, the other drive wheel 12 is lifted over the floor rather than being in contact with the floor. Therefore, as one drive wheel is lifted to roll in air, the robot cleaner cannot return to its normal state alone without users' help.
Further, the conventional robot cleaner has a problem that, since the power of the electric motor 17 is transferred through a gear train, that is, the transmission 18, noise due to gears and power loss can be produced, and a structure becomes complicated with possibly poor assemble, increasing the manufacturing cost, since wall members supporting the transmission 18 are additionally required.